package thinkingInJava.typeinfo.Proxy.NullClass_;

//: typeinfo/NullRobot.java
//Using a dynamic proxy to create a Null Object.
import java.lang.reflect.*;
import java.util.*;

class NullRobotProxyHandler implements InvocationHandler {
private String nullName;
private Robot proxied = new NRobot();
NullRobotProxyHandler(Class<? extends Robot> type) {
 nullName = type.getSimpleName() + " NullRobot";
}
private class NRobot implements Null, Robot {
 public String name() { return nullName; }
 public String model() { return nullName; }
 public List<Operation> operations() {
   return Collections.emptyList();
 }
}	
public Object
invoke(Object proxy, Method method, Object[] args)
throws Throwable {
 return method.invoke(proxied, args);
}
}

public class NullRobot {
public static Robot
newNullRobot(Class<? extends Robot> type) {
 return (Robot)Proxy.newProxyInstance(
   NullRobot.class.getClassLoader(),
   new Class[]{ Null.class, Robot.class },
   //new Class[]{ Robot.class }, // OK
   //new Class[]{ Null.class }, // java.lang.ClassCastException: com.sun.proxy.$Proxy0 cannot be cast to thinkingInJava.typeinfo.NullClass_.Robot
   new NullRobotProxyHandler(type));
}	
public static void main(String[] args) {
 Robot[] bots = {
   new SnowRemovalRobot("SnowBee"),
   newNullRobot(SnowRemovalRobot.class)
 };
 for(Robot bot : bots)
   Robot.Test.test(bot);
}
} /* Output:
Robot name: SnowBee
Robot model: SnowBot Series 11
SnowBee can shovel snow
SnowBee shoveling snow
SnowBee can chip ice
SnowBee chipping ice
SnowBee can clear the roof
SnowBee clearing roof
[Null Robot]
Robot name: SnowRemovalRobot NullRobot
Robot model: SnowRemovalRobot NullRobot
*///:~

